Lifting-magnet.



A. C.'EASTWOOD.

LIFTING MAGNET.

APBLIUATION FILED MAY 13, 1910.

1,01 5,728. Patented Jn. 23, 1912.

WITH ESQES INN "NR ARTHUR C. EA$TKVOO1L OF CLEVELAND, OHIO.

merino-MAGNET.

Specification of Letters Patent.

PatentedJan. 1912.

Application filed May 13, 1910. fierial l lo. 561,096.,

T 0 all whom it may concern:

Be-it known that I, ARTHUR C. EAs'r- WOOD, a citizen of the United States, residi gat Cleveland. in the county of Cuyalaga and State of Ohio, have invented new and useful Improvements in Lifting-lilag nets, f which the following is a specificatim and has special reference to electro-magnets designed for lifting and transporting magnetic materials and known as lifting magnets. Its object is so to construct the magnets that they are normally sealed against the entrance of moisture and that they automatically permit the escape of any gases or vapors generated in the magnet case. In the specification accompanying Letters Patent, No. 950,718, granted to me March 1, 1910, I set forth in some detail the manner in which moisture obtains access to the interior of lifting magnets, and described a n'ie'ans by which moisture may be excluded from the magnets and at the same time permit the heat-softened insulating material to expand freely. The present invention provides novel means for accomplishing the same results.

Electromagnets of the kind to which my invention applies are known as lifting magnets, and in service are suspended from the hook of a crane or other hdisting device and used forattracting and transporting magnetic material, the material being released from the magnet by opening the circuit of its magnetizing winding. With lifting magnets of large size the circuit of the winding is very highly inductive and a high lndllQfCl voltage occurs when the circuit of the ir agnet is opened, and as this occurs at very frequent intervals,,often as frequently as four times a minute, during the operation of the magnet, the insulation of the magnet is subjected to very frequent and severe electrical stresses. Further than this, such magnets are commonly used out of doors under all kinds (if-weather conditions, and are sub jected to a great amount of shock and abrasion when dropped upon piles of material to be handled or swung against piles of such material, cars, or other obstructions.

In order to keep the weight of the lifting magnet at a reasonable value. compared wi th the weight of material which the magnet will lift, it is necessary to make the winding as compact as possible. This neznvention relates to electromagnets cessitates a high current density in the winding and the dissipation of a large amountof eheat' from a restricted surface. In commercial lifting magnets of large size it is not uncommon todissipate much as 15000 watts as heat while the magnet in operation. In consequence of the high current density and large amount of heat to be dissipated, the windings of such commercial lifting magnets-are of necessity worked at,

temperatures very much higher than that ordinarily used inother electrical windings.

are not provided for the escape of these.

gases and vapors, pressure will be set up in the magnet case, which will eventually force an escape. My invention affords a simple and reliable means for permitting of the escape of such gases and vapors, at the same time automatically sealing the magnet case when the temperature of the magnet has been suitably reduced. Referring to the accompanying drawing,

Figure 1 is a perspective'of a lifting magnet containing my invention, and Fig. 2 is an enlarged section of Fig. 1 taken on the line IIII.

The magnet shown on the drawings has a great many of the features of the magnet shown on the drawings which form a part of Letters Patent. No. 928,510 granted to me July 20, 1909, and to such parts of the magnets shown on the drawings of this applicacation as are substantially the same in structure or function as corresponding parts shown on the drawings of thisipatent, I shallassign the same referencecharacters in order to facilitate a more ready understanding of the structure shownon the drawing of this application. but the precise structure shown 'is not essential to the present invention. as will be presently understood.

On the drawing A is an annular bottom plate preferably of brass provided withzthe inner and outer flanges a and a secured by screws to the lower face of the annular outer pole B and the inner pole C of the commodate the clamping means and bolts necteu per end of the magnet case or frame. The plate A is provided with the upwardly-projecting ange a serving as a mandrel, upon which the .coils e, 6 c and e are wound. The coil 6 rests on the insulating plate a which is seated on the plate A. The insulating plate a is placed above the coil 6 and the second coil 6 is woundso as to rest on the plate q. The coils e and a are placed above the coil 6 in a similar manner with insulating plates a between adjacent coils and above the top coil 6 gether in any desired manner, not shown, to cause the current to flow in series through the same.

Radial straps (only one, 8, being shown) are placed over the top plate a and are drawn down thereon by means of the screws or bolts (3 and (only one of each shown), the screws cZ' engaging in. bosses at the up flange a and the bolts d holes near the edge of the plate A. By these means the entire. winding containing several sections is'-firmly bound to the bottom plate A. The winding is afterward impregnated with. an insulating compound which will thoroughly waterproof .it.

The winding with all the parts assembled and clamped as hereinbefore described becomes a unit which may be moved about and assembled in the magnet case or frame, without danger of injury to the same. This unit is placed within the magnet frame and secured thereto by screws as shown in dotted lines,- Fig. 2. The walls of the magnet case are provided with pockets .3 to acpassingthrough suitable which engage the ends of these straps. The outer wearing plate D which I preferably make of manganese steel is then put in place and the pole shoe 0 secured to the outer face of the outer pole C by means of the bolts 0 The central pole shoe C is then secured to the face of the central pole B by means of the bolts 6 The terminals of the winding are brought up through opening 5/" and the insulating plate 9 and conin the recess-p above the plate 9? to the cable g leading to the supply lines for energizing the magnet, but before the plate 9 is put in place, a hot insulating sealing compound which hardens when cooled and softens when heated, is poured into the frame through the recesses 9 and g. In order to completely fill the space between the unit winding and the magnet frame with this compound, I admit current to thc winding and preferably apply heat,

externally to the magnet frame and bring the temperature of the magnet substantially to as high a temperature as it will reach in actual practice. Ellis causes the parts to expand and all moisture to be expelled. I

-=, pourin' the hot insulating com- The coils are connected tomagnet frame pound which thoroughly fills the vacant ,space within the frame and around the unit winding. As the magnet and the compound cool and contract, Isupply more of the insu lating compound so that when the magnet is cool, the space between the unit winding and the magnet frame is entirely filled with the compound. The compound is made to fill the recess 9 and the plate 9 is then secured above the recess by screws. The said insulating compound is designated by the letter 2'. f The recess 9 is provided with the insulating compound which covers the cable and Winding terminals. This recess is provided with the cover 9* bolted to the magnet frame. To this cover g I hinge the cover 9 which drops down into the recess g provided for the cable g, the cover having the slot 9 for the said cable.

I provide a number of ducts or vents o around the magnet, the vents leading preferably from the outer pockets s outwardly and downwardly through the wall of the and terminating between ad- The vents 4) allow the air to jacent ribs 7*.

the space between the unit escape from winding and the magnet casing when the insulating and sealing compound is poured in, and permits the compound to entirely fill the said space. Some of the compound will finally run out through .the vents. When the magnet cools, the compound in the vents will harden and seal them against the entrance of moisture. Y

If the magnet should be connected to the source of current supply for a longer period than it was designed to operate, such as being left energized all day or all night, or should be subjected to an abnormally high voltage, or by any accidental cause the temperature of the magnet should become higher than when the compound was put in, the vents c act as safety valves and allow some of the heated softened insulating compound and any vapors or gases formed within the magnet to escape. these "vents be not provided, the pressure within the magnet may become great enough to cause the compound to burst out through the recess 9 or through the joint between the plate A and the magnet poles of the magnet. The vents 11 opendownwardly so a heat-softening insulating and sealing material in the said vents and the space be tween the frame and the Winding, whereby when the temperature of the compound eX- weds a predetermined value a portion of Me me with any vapors and gas in the said space may escape and when the temperature declines to the said value the said material will serve to seal the vents against the entrance of moisture.

A lifting magnet, comprising a frame, a magnetizing Winding therein, there being outwardly and dow (wardly inclined ventsleading from the spzce in which the winding is seated through'the frame, and a heatsoftening insulating and sealing material ARTHUR O. EASTWOOD.

VVitnessesi H. M. DIEMER, H. S. RICHARDSON. 

